Gov. Mark Dayton said that the PolyMet copper-nickel mining project in northeastern Minnesota should be allowed to proceed if it meets environmental standards and financial safeguards, ending years of neutrality on one of the state’s most controversial private-sector projects.

“I’ve always believed environmental protection and economic growth can be complementary objectives,” Dayton said Tuesday after speaking at a cybersecurity conference in Minneapolis.

Dayton’s approval is no guarantee that the project, more than a decade in the making, will finally come to fruition. PolyMet first must obtain the necessary permits. The Department of Natural Resources is expected to issue a draft permit-to-mine by the end of the year, one of many permits necessary to begin the project. The draft permit would be followed by a public comment period of at least 52 days.

But Dayton’s support removes the chance that he would put up a roadblock. And he has provided crucial political cover to the agencies as they finalize their considerations about permitting.

Steve Morse, executive director of the Minnesota Environmental Partnership, said he and his allies “respectfully disagree” with Dayton’s stance, which he called “befuddling.”

“It’s a high-risk project in a highly sensitive watershed,” Morse said. “As Minnesotans, we ought to be protecting all of our water resources.”

Environmentalists fear toxic tailings could pollute the watershed and that water from open-pit mine and metal processing sites would have to be treated for decades after the mine closes, at a cost of millions.

Dayton’s public support for PolyMet comes at a critical time for the DFL Party, which is struggling to work through a series of thorny conflicts between environmentalists and building trades and other unions that support projects like PolyMet.

The project comes with the promise of 360 full-time, high-paying jobs — the kind that have grown scarce on the Iron Range as taconite mines have become more efficient, requiring fewer workers.

Dayton said he would insist that Minnesota taxpayers be protected in the event of environmental or financial calamity.

PolyMet is “owned by a Swiss company with a checkered record,” the governor said. “I want to make absolutely certain if the project is terminated, the people of Minnesota are not on the hook financially.”

Sen. David Tomassoni, DFL-Chisholm, applauded Dayton.

“I couldn’t be happier. I thought deep down he supported it. He waited until he got a comprehensive environmental impact statement. I think he sees it will be done within the law and can be done safely,” said Tomassoni, whose district is home to the processing plant. The mine itself sits in the district of DFL Senate Minority Leader Tom Bakk, DFL-Cook.

Tomassoni said Dayton’s public support showed he understands the problems facing the Iron Range, where population and job losses have hit hard in recent years.

Dayton was quick to distinguish the PolyMet project — on an old LTV Steel Mining site in Hoyt Lakes — from a different copper-nickel mine being mulled by Twin Metals, which is near the Boundary Waters Canoe Area Wilderness.

“Twin Metals might be the ultimate test” of his belief that economic growth and environmental protection can be complementary, Dayton said — because, he said, “I don’t see the compatibility.”

Morse said he is confused about how Dayton can favor one project and oppose the other. He cited the risks of environmental catastrophe outlined in a recent United Nations report on the failure of tailings dams, including the 2014 Mount Polley disaster in Canada.

Overall, Morse said, the risk of copper-nickel mining is not worth the reward. “It’s a high risk for a lot of people, for a limited number of jobs, for a limited period of time,” he said.

Environmentalists are unlikely to halt their campaign against PolyMet if the Dayton administration permits the project. Litigation in the courts is a strong possibility.